1. Field of the Invention
The present invention relates to an apparatus for purifying contaminated water or contaminated ground water and to a method of effectively purifying contaminated water or contaminated ground water by using the apparatus.
2. Related Background Art
With the recent advances in industrial technologies, a large amount of halogenated aliphatic hydrocarbon compounds (for example, chlorinated ethylene, chlorinated methane and others) have been used and their disposal and treatment have become a serious problem. Most of the environmental pollutants derived from chlorinated organic compounds will permeate into soil without decomposition and gradually dissolve in ground water to expand the contaminated area through ground water. Thus, it is strongly desired to establish a technology for purifying the contaminated environment to return it to the original state, in addition to never cause such serious pollution again.
In one method to purify ground water, the contaminated ground water is pumped up and purified on-site, by aerating the drawn ground water in an aeration tower to pass the pollutant into the gas phase. The pollutant in the gas phase is removed by an activated carbon column not to cause air pollution by directly releasing the gas into the air.
Purification methods utilizing degradation activities of microorganisms, i.e., bioremediation, have bean also proposed to purify ground water.
In connection with another purification method, Japanese Patent Application Laid-Open No. 54-66376 discloses an apparatus where a halide solution of NaCl or NaBr is electrolyzed in an electrolytic bath, and the original gas containing a malodorous component is passed through the catholyte and then through the anolyte to remove the smell. With such an apparatus, however, malodorous gas may not be treated steadily, because it includes three steps of aeration in the anolyte, recovery of the gas, and aeration in the catholyte in the process.
Japanese Patent Publication No. 53-17816 discloses a method of treating an organic waste liquid, where aluminum chloride or iron chloride is dissolved in the organic waste solution and the chloride is electrolyzed under UV irradiation. According to the specification, hypochlorous acid is generated from the electrolyzed chloride and the organic compounds in the waste are decomposed by active oxygen generated from hypochlorous acid by UV irradiation.
This method also might not achieve a steady treatment, since the chloride compound concentration in the waste will vary.
It is also known that a functional water can be obtained by electrolyzing water. For example, acidic electrolyzed water has sterilizing properties (Japanese Patent Application Laid-Open No. 1-180293) or can cleanse contaminants on semiconductor wafers (EP 605882A).
Photodecomposition is also known. For example, Japanese Patent Application Laid-Open No. 9-299753 and No. 10-180040 disclose a photodecomposition apparatus utilizing a phenomenon that UV-B, and C can decompose certain pollutants.
The object of the present invention is to provide an apparatus that can effectively purify contaminated water including ground water, without secondary pollution problems, and not requiring activated carbon or microorganisms. Another object of the present invention is to provide a purification method using the apparatus.
One aspect of the present invention is an apparatus for purifying contaminated water such as ground water.
According to one aspect of the present invention, there is provided a purifying apparatus for water containing a pollutant comprising:
an aerator in which a contaminated water containing a pollutant is aerated with a gas to generate a gas containing the pollutant;
a chlorine-containing gas generator that generates a chlorine-containing gas;
a mixing section where the pollutant-containing gas generated from the contaminated water and the chlorine-containing gas generated in the chlorine-containing gas generator are mixed; and
light-irradiation means for irradiating the mixed gas with light to decompose the pollutant contained in the mixed gas.
The purification apparatus for contaminated water of the present invention is desirably constituted so that the aerator is in a well.
The chlorine-containing gas generator that generates a chlorine-containing gas includes, in addition to a chlorine cylinder, aerators to aerate a functional water that generates chlorine-containing gas by aeration. Specifically, an aerator to blow air to the surface of the functional water, a jet device to contacting the spray of functional water from a nozzle into contact with air, or a bubbler can be preferably used.
The chlorine-containing gas generator may comprise a water tank, means for generating functional water, means for introducing air into the water tank, means for discharging a chlorine-containing gas generated, and means for discharging the functional water used for generating a chlorine-containing gas.
The means for generating functional water may comprise a water tank, means for feeding an electrolyte-containing water into the water tank, and a pair of electrodes and a power source to apply an electric potential to the electrolyte-containing water in the water tank.
According to another aspect of the present invention, there is provided a method for purifying contaminated water comprising the steps of:
obtaining a pollutant-containing gas by aerating a contaminated water containing a pollutant;
obtaining a chlorine-containing gas;
mixing the pollutant-containing gas and the chlorine-containing gas to form a mixed gas;
decomposing the pollutant in the mixed gas by irradiating with light the mixed gas introduced into a treatment region in a treatment tank: and
discharging the mixed gas after decomposition treatment from the treatment region.